The Transgenic Mouse Core Facility (TMCF) is a newly established (January 1998) state-of-the-art facility that serves the Purdue University Cancer Center research community. The TMCF offers three basic services; (l) pronuclear injections for the production of transgenic mice, (2) generation of targeted ES cell lines and (3) blastocyst injections to generate chimeric mice for producing homozygous null animal models. The ability to introduce foreign genes into the mammalian germ line, or to selectively ablate endogenous genes from the mouse genome, has proven to be one of the most powerful experimental tools to understand specific genetic requirements for both developmental and tumor promoting regulatory pathways. These techniques have been enormously useful in elucidating mechanisms of gene regulation and protein function. In the area of oncology, transgenic mice have been used to demonstrate that overexpression of protooncogenes can predispose cells to develop malignant tumors, show that aberrant expression of oncogenes can transform tissues normally resistant to neoplastic degeneration, and reveal the requirement for tumor suppressor genes to maintain normal growth control. Transgenic strategies also have revolutionized the way we approach the complex problems associated with carcinogenesis, including issues related to gene regulation, cell-cell interactions, cell cycle control and a variety of signal transduction pathways. The Purdue University Cancer Center has been an integral component of our cancer research community, fostering close interactions among active scientists in understanding aspects of experimental therapeutics, structural biology, cell differentiation and gene regulation. The role of the TMCF is to assist the individual investigators and Program Areas within the Cancer Center that are seeking novel approaches in addressing a variety of cancer related issues. In offering these key transgenic services, the TMCF provides the needed expertise to our investigators to help them address future challenges in their cancer research.